- Volume 35, Issue 2, 1991

Summary. The clinical isolate Staphylococcus aureus WBG1024 was resistant to cadmium, benzyl penicillin, kanamycin, neomycin, streptomycin, tetracycline and trimethoprim and harboured a conjugative plasmid pWBG637 (34.5 kb) and non-conjugative plasmids of 23.8, 4.4, 2.8 and 1.9 kb. Transduction and mixed-culture transfer experiments demonstrated that the 4.4-kb plasmid (pWBG632) encoded resistance to tetracycline and the 23.8-kb plasmid (pWBG628) encoded resistance to cadmium, benzyl penicillin, kanamycin, neomycin and streptomycin. The conjugative plasmid pWBG637 was able to mobilise a further 4.4-kb plasmid (pWBG633) encoding streptomycin resistance and recombined with the multiresistance plasmid pWBG628 to produce transconjugants of various resistance phenotypes.

Summary. Fifty-nine epidemiologically unrelated methicillin-resistant Staphylococcus aureus (MRSA) isolates from different geographical areas and 23 phage-type 77 MRSA isolates from France were investigated. Cellular DNA, digested with restriction endonucleases EcoRI or HindIII, was probed with plasmids carrying the gene encoding 16S rRNA (pBA2), the gene aacA-aphD (pSF815A) and the gene aacA-aphD plus part of IS256 (pIP 1307). When probed with pBA2, most of the unrelated isolates displayed the same hybridisation pattern. A greater diversity in patterns was detected in gentamicin-resistant strains with the two other probes. The most accurate fingerprinting of these isolates was obtained with the probe pIP 1307. Moreover, this probe appeared to be useful for tracing the phage-type 77 epidemic MRSA isolates widespread in French hospitals.

Summary. The susceptibility of 72 mycoplasmas to a range of antimicrobial agents was assessed in a 6-h ATP bioluminescence system. ATP was assayed with the Amerlite Analyser. Correlation with conventionally determined MICs was excellent for erythromycin and tetracycline even at 3 h. However, for ciprofloxacin, correlation was poor unless incubation was extended to 6 h.

Summary. The adherence of Serratia marcescens to bladder epithelial cells of mice with alloxan-induced diabetes was studied. S. marcescens adhered more strongly to the bladder epithelial cells of diabetic mice than to those of normal mice both in vitro and in vivo. The susceptibility of diabetic mice to urinary tract infection may be due to an increased adhesive capacity of bladder epithelial cells.

Summary. The polymerase chain reaction (PCR) was used to amplify specific DNA sequences from different clinical isolates of Borrelia burgdorferi and from cerebrospinal fluid (CSF) of two patients with Lyme disease of the central nervous system. The amplification products were separated by polyacrylamide gel electrophoresis and visualised by ethidium bromide staining. The definitive identification of amplified DNA as a part of the B. burgdorferi flagellin gene was achieved by hybridisation to a 40-base oligonucleotide probe complementary to a part of the spirochaetal gene but not to the primers. Attempts to cultivate borreliae from either patient were unsuccessful and one patient had no serological marker in serum or CSF to indicate borreliosis. Clinical symptoms of both patients regressed with antibiotic therapy. The PCR system is a powerful and rapid technique to amplify flagellin gene sequences from CSF of patients with neuroborreliosis. Only one-tenth of the time needed for cultivation was required from CSF sampling to diagnosis. Gene amplification might, for the first time, allow effective monitoring of therapy for patients with Lyme disease of the central nervous system.

Summary. The diagnosis of bacterial vaginosis (BV) by direct gram-stained smear of vaginal discharge was evaluated in 90 consecutive patients. Vaginal secretions from 20 healthy female volunteers were also examined. All specimens were examined by culture for growth of Gardnerella vaginalis and Lactobacillus spp. Only 35 (38.9%) of the patients with vaginal discharge satisfied the clinical diagnosis of BV. The vaginal gram-stained smear from all these 35 patients contained typical gardnerella morphotypes characteristic of BV and G. vaginalis was isolated from all of them as well as from a further 10 patients who did not satisfy the criteria for diagnosis of BV. The semi-quantitative assessment of gardnerella morphotypes was found to correlate positively with the semi-quantitative assessment of G. vaginalis growth by culture (p < 0.0001). There was a strong inverse relationship between the quantity of lactobacillus and gardnerella morphotypes. Direct gram-staining of smears should facilitate the diagnosis of BV for clinicians with minimum need for confirmation by culture, particularly in a third world setting with few or no laboratory facilities.

Summary. Sorbitol-MacConkey medium has become widely used for the isolation of verotoxigenic (VT+) Escherichia coli O157. However, many organisms other than VT+ E. coli O157, especially other serogroups of E. coli and Proteus spp., may not ferment sorbitol, and thus may be confused initially with VT+ E. coli O157. Rhamnose is not fermented by VT+ E. coli O157, but is by most sorbitol non-fermenting E. coli of other serogroups. Cefixime is a cephalosporin antibiotic that is more active against Proteus spp. than against E. coli. Inclusion of rhamnose and cefixime in sorbitol-MacConkey agar improves its selectivity for the isolation of VT+ E. coli O157.

Summary. As few as five of the species of bacteria commonly found in human faeces–Escherichia coli, Enterobacter aerogenes, Enterococcus faecalis, Bacteroides ovatus and Fusobacterium varium—when grown together in anaerobic continuous flow cultures exerted antagonistic effects on Salmonella typhimurium as great as those given by mixed bacteria from extracts of human faeces. In a single culture, the population of S. typhimurium was c. 108 cfu/ml but in mixed cultures with the five antagonistic bacteria or mixed faecal bacteria it was reduced to c. 103 cfu/ml. Antagonism appeared to be the result of competition for the growth limiting amino acids, arginine, serine, threonine and aspartic acid. Optimal manifestation of antagonism required the presence of carbon sources fermentable only by antagonistic bacteria, such as lactose 0.1%, w/v, sucrose 0.1% (w/v) and starch 0.2-0.3% w/v. These carbohydrates promoted the growth of the antagonistic bacteria, particularly E. coli and B. ovatus. However, an increase in concentration by several fold of any one of four growth-limiting amino acids in the medium diminished the antagonistic effects and the population of S. typhimurium rose 102-103-fold.

Summary. Representative strains of 22 serotypes of the fragilis group of Bacteroides and four non-fragilis control strains of B. melaninogenicus, B. disiens, B. bivius and Fusobacterium nucleatum were tested by SDS-PAGE and immunoblotting with hyperimmune rabbit sera. SDS-PAGE showed 25 polypeptide bands but, after immunoblotting, 24 antigenic bands were observed in various combinations in all the strains. Three of these were detected only in the control strains, whereas six others were present in different combinations in all strains of the fragilis group but were not present in the controls. Cluster analysis of the antigenic bands showed that the controls were antigenically different from the fragilis group strains. Strains of the fragilis group from the same geographic localities grouped in single clusters; most faecal isolates and NCTC strains appeared separate. There was no correlation between the species of Bacteroides and their antigenic structure. SDS-PAGE with immunoblotting is a superior technique for typing the fragilis group of Bacteroides. Specific antigens have been identified which may be used in the serodiagnosis of infection with these organisms.